The field of this invention is mechanisms that can hold open a subsurface safety valve (SSSV) that has malfunctioned so that another valve can be installed to take its place.
SSSVs are normally closed valves that are used primarily in offshore and gas wells to prevent uncontrollable flow of fluid to the surface, in the event the surface safety equipment fails to properly operate. If the SSSV malfunctions or for any other reason requires replacement with a backup SSSV, the well operator will normally want the old SSSV locked in the open position so it does not interfere with well operations after the old SSV has been taken out of service. Typically, to avoid undue complication in the design and operation of an SSSV, the lock open assembly is not installed with the SSSV but is subsequently run in when needed on an accessory tool known as a flapper lock open (FLO) tool.
One known design of an FLO tool is U.S. Pat. No. 4,577,694, which illustrates the use of a scroll of wound spring steel that is allowed to spring out after being delivered to the SSSV to keep the flapper from rotating back to a closed position. The downside of this design and several others is that flow through the locked open SSSV could and did, at times, dislodge the lock open device, allowing the flapper to close off the well. In this particular patent, the ring of steel was coiled, like a watch spring and held at opposite ends until properly positioned. When the delivery tool released the ring, it sprang outwardly to contact the flapper. This tool was complicated and required stocking of various sizes of rings as well as an installation method that involved two wireline trips with jar down/jar up activation.
Another technique, shown in U.S. Pat. No. 5,574,889 required that the flow tube be engaged and forcibly moved down to get the flapper into the open position. After that one or more indentations were made in the flow tube, which could engage a shoulder and prevent the flow tube from returning to the flapper-closed position. This device had several disadvantages. The flow tube was permanently damaged. The tool required enough force to overcome bias on the flow tube to push it into the flapper open position. Finally, part of the procedure required pumping fluid under pressure into the well, which could adversely affect subsequent production.
Another technique, shown in U.S. Pat. No. 5,564,675, the flow tube is forcibly engaged and pushed so far down that the actuating piston comes out of its seal bore in a manner as to wedge the flow tube in the flapper open position. This design has similar disadvantages as U.S. Pat. No. 5,574,889 and a further disadvantage that flow communication to the control system occurs due to operation of this lock open device.
Another technique illustrated in U.S. Pat. No. 6,059,041, forces the flow tube down and releases an expandable tube to hold the flapper open. Similar, disadvantages as the previous two techniques are realized in this design.
Other art in the area of lock open devices for SSSVs includes U.S. Pat. Nos. 3,786,866; 4,344,602; 4,967,845; 4,624,315 and 4,457,379. Of more general interest are U.S. Pat. Nos. 5,040,283(using a shape memory metal for downhole patches); 4,846,281; 4,760,879; 4,729,432; 4,566,541 and 4,213,508.
One of the objectives of the present invention is to deliver and set a hold open device in an SSSV in a manner that it will not become dislodged. The technique to accomplish this objective comprises using an expansion of a tubular member so as to deform it into position where it will prevent a flow tube from returning to the flapper closed position or to actually use the expanded structure directly against the flapper when it is held open by the flow tube. Those skilled in the art will have a clearer understanding of the various embodiments for accomplishing the objective of holding an SSSV in an open position from the detailed description of the preferred embodiment and the claims, which appear below.
Various techniques for holding open an SSSV using expansion technology are disclosed. A sleeve is delivered to the SSSV and expanded mechanically or hydraulically to deposit the deformed sleeve in position over a flapper or against a flow tube holding the flapper in the open position.